Ascent: An Agentic System over the Model Context Protocol for Real-World Clinical Data Analysis
Organizations: Bayer AG, Germany
Abstract
Answering epidemiological questions from real-world clinical data requires medical coding, schema-aware SQL, and validation of implicit choices about populations, denominators, and time. We present Ascent, an agentic system that exposes medical coding, question answering, and cohort analysis through a shared Model Context Protocol tool surface for standardized and native schemas. We introduce EpiTrap, a dataset testing whether systems avoid recognized pharmacoepidemiological errors, and compare a fixed pipeline with agents across models and orchestrators. With capable models, agents improve accuracy over the fixed pipeline by an average of 27 and 20 percentage points on native and standardized schemas, respectively. These gains require more tool calls and longer runtimes. Experience from real projects highlights the system's value for feasibility assessment, diagnostic iteration, and expert-guided analysis.
Figures & tables
| Question (system sees only this) | The recognized error the reasoning must avoid |
|---|---|
| Count patients with severe hyperglycemia (blood glucose above 250 mg/dL) at any measurement. | Unit harmonization. Glucose is recorded in mixed units, so applying one threshold to raw values misclassifies measurements. Correct: harmonize units, remove implausible values, then apply the threshold. |
| Estimate the one-year incidence of gout among adults with at least one year of continuous enrollment. | Prevalence–incidence conflation. A pre-existing gout diagnosis is not an incident case. Correct: exclude prevalent cases via a baseline washout. |
| Measure the cervical-cancer screening rate among adult women. | Denominator ineligibility. Women with documented absence of the cervix (e.g. following total hysterectomy) are ineligible for routine screening. Correct: exclude them from the denominator using prior diagnoses and procedures. |
| Native, | OMOP, | |||||
| Configuration | Acc. | Time | Calls | Acc. | Time | Calls |
| Baseline: no agent loop, no framework | ||||||
| mech. pipeline | 50% | 231 s | 3.0 | 49% | 180 s | 3.0 |
| Claude Agent SDK | ||||||
| Sonnet 5, plain | 75% | 565 s | 9.4 | 75% | 275 s | 8.8 |
| no scaffold | 76% | 197 s | 16.8 | 84% | 177 s | 18.6 |
Data Analysis Agents
Data analysis agents use language models and tools to explore datasets, run analyses, and produce answers or reports grounded in evidence.
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